It has heretofore been proposed to monitor the relative velocity between relatively movable components of an automobile or similar vehicle by means of a linear velocity transducer mounted in parallel relationship to a damper interconnecting the vehicle components. Such a transducer typically consists of an outer tubular member that is connected to one of the relatively movable vehicle components and has two serially connected and oppositely-wound coils at spaced locations along its length; and an inner permanent magnet member that is connected to the other of the vehicle components and is located within the outer member. Relative movement between the vehicle components causes corresponding relative movement between the inner and outer transducer members. This generates a voltage in the coils which is proportional to the rate of such movement, and thus to the relative velocity between the vehicle components. Two coils wound in series-opposing relationship are employed since if only a single coil were used, the net voltage would be zero when, as is normally the case, both poles of the magnetic inner member are within the coil.
Another linear velocity transducer that has been previously used, at least experimentally, includes an outer tubular member having a single coil, and an elongate magnet that projects into and from the outer member and is axially movable relative to it. The length of the magnet and of the strokes of relative movement between it and the other member are such that the magnetic pole upon the end of the magnet distal from the outer member never enters the coil of the latter.
U.S. Pat. No. 4,351,515 discloses a velocity transducer associated with a vehicle damper of the type employing solid particles, rather than a fluid, as the damping medium. A permanent magnet is mounted upon an inner member of the damper, and a coil is mounted upon an outer member of the damper. Relative axial movement between the inner and outer damper members generates electrical current in the coil, and this is used to change the intensity of a magnetic field that varies the freedom of movement of the solid particles of the damper.
Apart from and in contrast to passive transducers that monitor or detect relative velocity, there are also active transducers of the "inductance" type that are directly associated with dampers and that detect changes in displacement or position of the relatively movable vehicle components. Illustrative of these active induction-type position sensors are those disclosed in U.S. Pat. Nos. 4,502,006, 4,638,670 and 4,802,657, and in a publication entitled "Lucas Automotive-Sensors. "
In addition to the foregoing art, U.S. Pat. Nos. 4,365,513, 4,132,980 and 4,080,592 may be of interest relative to the present invention.